DESCRIPTION

Zsh is a UNIX command interpreter (shell) usable as an interactive
login shell and as a shell script command processor. Of the standard
shells, zsh most closely resembles ksh but includes many enhancements.
Zsh has command line editing, builtin spelling correction, programmable
command completion, shell functions (with autoloading), a history mech-
anism, and a host of other features.

AUTHOR

Zsh was originally written by Paul Falstad <pf@zsh.org>. Zsh is now
maintained by the members of the zsh-workers mailing list <zsh-work-ers@sunsite.dk>. The development is currently coordinated by Peter
Stephenson <pws@zsh.org>. The coordinator can be contacted at <coordi-nator@zsh.org>, but matters relating to the code should generally go to
the mailing list.

MAILING LISTS

Zsh has 3 mailing lists:
<zsh-announce@sunsite.dk>
Announcements about releases, major changes in the shell and the
monthly posting of the Zsh FAQ. (moderated)
<zsh-users@sunsite.dk>
User discussions.
<zsh-workers@sunsite.dk>
Hacking, development, bug reports and patches.
To subscribe or unsubscribe, send mail to the associated administrative
address for the mailing list.
<zsh-announce-subscribe@sunsite.dk><zsh-users-subscribe@sunsite.dk><zsh-workers-subscribe@sunsite.dk><zsh-announce-unsubscribe@sunsite.dk><zsh-users-unsubscribe@sunsite.dk><zsh-workers-unsubscribe@sunsite.dk>
YOU ONLY NEED TO JOIN ONE OF THE MAILING LISTS AS THEY ARE NESTED. All
submissions to zsh-announce are automatically forwarded to zsh-users.
All submissions to zsh-users are automatically forwarded to zsh-work-ers.
If you have problems subscribing/unsubscribing to any of the mailing
lists, send mail to <listmaster@zsh.org>. The mailing lists are main-
tained by Karsten Thygesen <karthy@kom.auc.dk>.
The mailing lists are archived; the archives can be accessed via the
administrative addresses listed above. There is also a hypertext
archive, maintained by Geoff Wing <gcw@zsh.org>, available at
http://www.zsh.org/mla/.

THE ZSH FAQ

Zsh has a list of Frequently Asked Questions (FAQ), maintained by Peter
Stephenson <pws@zsh.org>. It is regularly posted to the newsgroup
comp.unix.shell and the zsh-announce mailing list. The latest version
can be found at any of the Zsh FTP sites, or at
http://www.zsh.org/FAQ/. The contact address for FAQ-related matters
is <faqmaster@zsh.org>.

THE ZSH WEB PAGE

Zsh has a web page which is located at http://www.zsh.org/. This is
maintained by Karsten Thygesen <karthy@zsh.org>, of SunSITE Denmark.
The contact address for web-related matters is <webmaster@zsh.org>.

THE ZSH USERGUIDE

A userguide is currently in preparation. It is intended to complement
the manual, with explanations and hints on issues where the manual can
be cabbalistic, hierographic, or downright mystifying (for example, the
word ‘hierographic’ does not exist). It can be viewed in its current
state at http://zsh.sunsite.dk/Guide/. At the time of writing, chap-
ters dealing with startup files and their contents and the new comple-
tion system were essentially complete.

THE ZSH WIKI

A ‘wiki’ website for zsh has been created at http://www.zshwiki.org/.
This is a site which can be added to and modified directly by users
without any special permission. You can add your own zsh tips and con-
figurations.

INVOCATION OPTIONS

The following flags are interpreted by the shell when invoked to deter-
mine where the shell will read commands from:
-c Take the first argument as a command to execute, rather than
reading commands from a script or standard input. If any fur-
ther arguments are given, the first one is assigned to $0,
rather than being used as a positional parameter.
-i Force shell to be interactive.
-s Force shell to read commands from the standard input. If the -s
flag is not present and an argument is given, the first argument
is taken to be the pathname of a script to execute.
After the first one or two arguments have been appropriated as
described above, the remaining arguments are assigned to the positional
parameters.
For further options, which are common to invocation and the set
builtin, see zshoptions(1).
Options may be specified by name using the -o option. -o acts like a
single-letter option, but takes a following string as the option name.
For example,
zsh-x-oshwordsplitscr
runs the script scr, setting the XTRACE option by the corresponding
letter ‘-x’ and the SH_WORD_SPLIT option by name. Options may be
turned off by name by using +o instead of -o. -o can be stacked up
with preceding single-letter options, so for example ‘-xoshwordsplit’
or ‘-xoshwordsplit’ is equivalent to ‘-x-oshwordsplit’.
Options may also be specified by name in GNU long option style,
‘--option-name’. When this is done, ‘-’ characters in the option name
are permitted: they are translated into ‘_’, and thus ignored. So, for
example, ‘zsh--sh-word-split’ invokes zsh with the SH_WORD_SPLIT
option turned on. Like other option syntaxes, options can be turned
off by replacing the initial ‘-’ with a ‘+’; thus ‘+-sh-word-split’ is
equivalent to ‘--no-sh-word-split’. Unlike other option syntaxes,
GNU-style long options cannot be stacked with any other options, so for
example ‘-x-shwordsplit’ is an error, rather than being treated like
‘-x--shwordsplit’.
The special GNU-style option ‘--version’ is handled; it sends to stan-
dard output the shell’s version information, then exits successfully.
‘--help’ is also handled; it sends to standard output a list of options
that can be used when invoking the shell, then exits successfully.
Option processing may be finished, allowing following arguments that
start with ‘-’ or ‘+’ to be treated as normal arguments, in two ways.
Firstly, a lone ‘-’ (or ‘+’) as an argument by itself ends option pro-
cessing. Secondly, a special option ‘--’ (or ‘+-’), which may be spec-
ified on its own (which is the standard POSIX usage) or may be stacked
with preceding options (so ‘-x-’ is equivalent to ‘-x--’). Options
are not permitted to be stacked after ‘--’ (so ‘-x-f’ is an error), but
note the GNU-style option form discussed above, where ‘--shwordsplit’
is permitted and does not end option processing.
Except when the sh/ksh emulation single-letter options are in effect,
the option ‘-b’ (or ‘+b’) ends option processing. ‘-b’ is like ‘--’,
except that further single-letter options can be stacked after the ‘-b’
and will take effect as normal.

COMPATIBILITY

Zsh tries to emulate sh or ksh when it is invoked as sh or ksh respec-
tively; more precisely, it looks at the first letter of the name by
which it was invoked, excluding any initial ‘r’ (assumed to stand for
‘restricted’), and if that is ‘s’ or ‘k’ it will emulate sh or ksh.
Furthermore, if invoked as su (which happens on certain systems when
the shell is executed by the su command), the shell will try to find an
alternative name from the SHELL environment variable and perform emula-
tion based on that.
In sh and ksh compatibility modes the following parameters are not spe-
cial and not initialized by the shell: ARGC, argv, cdpath, fignore,
fpath, HISTCHARS, mailpath, MANPATH, manpath, path, prompt, PROMPT,
PROMPT2, PROMPT3, PROMPT4, psvar, status, watch.
The usual zsh startup/shutdown scripts are not executed. Login shells
source /etc/profile followed by $HOME/.profile. If the ENV environment
variable is set on invocation, $ENV is sourced after the profile
scripts. The value of ENV is subjected to parameter expansion, command
substitution, and arithmetic expansion before being interpreted as a
pathname. Note that the PRIVILEGED option also affects the execution
of startup files.
The following options are set if the shell is invoked as sh or ksh:
NO_BAD_PATTERN, NO_BANG_HIST, NO_BG_NICE, NO_EQUALS, NO_FUNC-TION_ARGZERO, GLOB_SUBST, NO_GLOBAL_EXPORT, NO_HUP, INTERACTIVE_COM-MENTS, KSH_ARRAYS, NO_MULTIOS, NO_NOMATCH, NO_NOTIFY, POSIX_BUILTINS,
NO_PROMPT_PERCENT, RM_STAR_SILENT, SH_FILE_EXPANSION, SH_GLOB,
SH_OPTION_LETTERS, SH_WORD_SPLIT. Additionally the BSD_ECHO and
IGNORE_BRACES options are set if zsh is invoked as sh. Also, the
KSH_OPTION_PRINT, LOCAL_OPTIONS, PROMPT_BANG, PROMPT_SUBST and SIN-GLE_LINE_ZLE options are set if zsh is invoked as ksh.

RESTRICTED SHELL

When the basename of the command used to invoke zsh starts with the
letter ‘r’ or the ‘-r’ command line option is supplied at invocation,
the shell becomes restricted. Emulation mode is determined after
stripping the letter ‘r’ from the invocation name. The following are
disabled in restricted mode:
· changing directories with the cd builtin
· changing or unsetting the PATH, path, MODULE_PATH, module_path,
SHELL, HISTFILE, HISTSIZE, GID, EGID, UID, EUID, USERNAME,
LD_LIBRARY_PATH, LD_AOUT_LIBRARY_PATH, LD_PRELOAD and
LD_AOUT_PRELOAD parameters
· specifying command names containing /
· specifying command pathnames using hash
· redirecting output to files
· using the exec builtin command to replace the shell with another
command
· using jobs-Z to overwrite the shell process’ argument and envi-
ronment space
· using the ARGV0 parameter to override argv[0] for external com-
mands
· turning off restricted mode with set+r or unsetoptRESTRICTED
These restrictions are enforced after processing the startup files.
The startup files should set up PATH to point to a directory of com-
mands which can be safely invoked in the restricted environment. They
may also add further restrictions by disabling selected builtins.
Restricted mode can also be activated any time by setting the
RESTRICTED option. This immediately enables all the restrictions
described above even if the shell still has not processed all startup
files.

STARTUP/SHUTDOWN FILES

Commands are first read from /etc/zshenv; this cannot be overridden.
Subsequent behaviour is modified by the RCS and GLOBAL_RCS options; the
former affects all startup files, while the second only affects those
in the /etc directory. If one of the options is unset at any point,
any subsequent startup file(s) of the corresponding type will not be
read. It is also possible for a file in $ZDOTDIR to re-enable
GLOBAL_RCS. Both RCS and GLOBAL_RCS are set by default.
Commands are then read from $ZDOTDIR/.zshenv. If the shell is a login
shell, commands are read from /etc/zprofile and then $ZDOTDIR/.zpro-file. Then, if the shell is interactive, commands are read from
/etc/zshrc and then $ZDOTDIR/.zshrc. Finally, if the shell is a login
shell, /etc/zlogin and $ZDOTDIR/.zlogin are read.
When a login shell exits, the files $ZDOTDIR/.zlogout and then
/etc/zlogout are read. This happens with either an explicit exit via
the exit or logout commands, or an implicit exit by reading end-of-file
from the terminal. However, if the shell terminates due to exec’ing
another process, the logout files are not read. These are also
affected by the RCS and GLOBAL_RCS options. Note also that the RCS
option affects the saving of history files, i.e. if RCS is unset when
the shell exits, no history file will be saved.
If ZDOTDIR is unset, HOME is used instead. Those files listed above as
being in /etc may be in another directory, depending on the installa-
tion.
As /etc/zshenv is run for all instances of zsh, it is important that it
be kept as small as possible. In particular, it is a good idea to put
code that does not need to be run for every single shell behind a test
of the form ‘if[[-orcs]];then...’ so that it will not be executed
when zsh is invoked with the ‘-f’ option.
Any of these files may be pre-compiled with the zcompile builtin com-
mand (see zshbuiltins(1)). If a compiled file exists (named for the
original file plus the .zwc extension) and it is newer than the origi-
nal file, the compiled file will be used instead.